‘Dirty 30’ and its toxic siblings: the most dangerous parts of the Sellafield nuclear site

Radioactive sludge

In the early 1950s, a huge hole was dug into the Cumbrian coast and lined with concrete. Roughly the length of three Olympic swimming pools and known as B30, it was built to hold skip loads of spent nuclear fuel.

Those highly radioactive rods came from the 26 Magnox nuclear reactors that helped keep Britain’s lights on between 1956 and 2015. When B30 was first put to work, it was designed to keep the fuel rods submerged for only three months before reprocessing work was carried out.

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But when 1970s miners’ strikes shut down coal power stations and forced greater reliance on nuclear plants, more spent fuel than could be quickly reprocessed was generated. The silos and ponds, built to prevent airborne contamination if the fuel or radioactive sludge dried out, rapidly filled up. Meanwhile, the fuel corroded in the water, breaking down into radioactive sludge.

Debris from elsewhere within Sellafield was later added and the pond was abandoned when new facilities were built in 1986, clouding over and leaving workers on site with little idea what lay beneath its murky waters.

A nightmare job with no blueprint’

In 2014, photos of B30 and nearby B29 leaked via an anonymous source to the Ecologist led to concerns over the radioactive risk associated with the poor repair of the ponds.

The two facilities were used until the mid-1970s for short-term storage of spent fuel until it could be reprocessed and used for producing plutonium for the military.

The Ecologist pictures showed hundreds of highly radioactive fuel rods in ponds housed within cracked concrete overgrown with weeds, with seagulls bathing in the water. The images, taken over a period of seven years, led the nuclear safety expert John Large to warn that any breach of the wall would “give rise to a very big radioactive release”.

At the time, the Office for Nuclear Regulation (ONR), the nuclear safety regulator, said that while the old ponds bring “significant challenges”, their appearance “does not mean that operations and activities on those facilities are unsafe”.

Empty nuclear fuel skips in the first generation Magnox storage pond
The B30 pond carries a higher risk of radiation than other parts of the site. Photograph:

It took 15 years and £1.5bn to bring B30 to a point where decommissioning could begin several years ago, with builders limited to working only half an hour a day close to the pool to prevent them from exceeding radiation exposure limits. Remotely operated vehicles, normally used to help with submarine rescues, were originally deployed but quickly failed, often within hours, because of the overpowering radiation. Newer models have since been used to vacuum up nuclear sludge, which is then moved to alternative long-term storage.

Sellafield hopes to have drained the pond by the early 2030s, and demolished it by the 2050s.

A new facility, the sludge packaging plant, has been built to receive radioactive sludge from B30. The nuclear watchdog said there have been some “regulatory challenges along the way … including noncompliance with fire regulations”.

Although the reservoir is still nicknamed “Dirty 30”, it was officially rebranded in 2018 as the First Generation Magnox storage pond.

Magnox swarf storage silo diagram

But one former longstanding employee says that, despite the cracks, the contents of the ponds are gradually improving: “I have seen it at its worst. The water quality was horrendous; you could stand on the roof and look down and not see a single thing in there.

“In the control room, there are a group of lads using PlayStation-like controls for robots to pick up bits the size of a 50p piece and hoover up the sludge. It’s cutting edge.”

He adds: “[Decommissioning Sellafield] is the biggest job in nuclear and there is no blueprint. It’s a dream and a nightmare job. There has been real progress – every skip that comes out makes it safer and reduces the hazard risk.”

The pile fuel storage pond at Sellafield
The pile fuel storage pond, which is on a separate part of the site from the Magnox storage. Photograph: Bloomberg/Getty Images

Toxic neighbours

B30 sits in a “separation zone” that requires greater security checks, and carries a higher risk of radiation, than the rest of the town-sized site. Although B30 is the most notorious crumbling building on Sellafield’s sprawling estate, it is far from the only problem child.

Nearby is B38, used to store highly radioactive cladding from reactor fuel rods. It was also used heavily during the miners’ strike of 1972, when nuclear plants were relied on to produce extra power, and it proved impossible to process all the waste that was being generated. Two years later, the public’s view of the nuclear industry was sharpened by the launch of the Protect and Survive advice on surviving a nuclear attack.

In B29 lie the toxic remains of Britain’s attempt to become an atomic superpower during the cold war.

A radiation warning sign on a railing near the pile fuel storage pond
A radiation warning sign on a railing near the pile fuel storage pond. Photograph: Bloomberg/Getty Images

Windscale, a former munitions factory, was selected to host the first atomic reactors, known as Pile 1 and Pile 2, after the second world war. They produced plutonium for nuclear weapons, and efforts were rushed through to allow Britain to explode its own atomic bombs by 1952.

The toxic waste from this programme was stored in B29 – which stretched between Piles 1 and 2 – and a massive silo, B41. There have been efforts to secure and remove the waste in B41 in recent years.

There are also grave concerns over leaks from the Magnox swarf storage silo (MSSS), described as “one of the highest-hazard nuclear facilities in the UK”. It was constructed as a radioactive waste store in four stages between 1964 and 1983 and has not been in active use since the 1990s. The waste is stored under water to prevent ignition and to maintain constant temperatures.

The silo was first found to be leaking radioactive water into the ground in the 1970s and there are concerns that work to retrieve the waste, planned over the next three decades, has the “potential to reopen historic leak paths” and introduce new ones, according to the ONR.

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Earlier this year, the ONR warned that a leak from the MSSS was likely to continue to 2050, with “potentially significant consequences” if it gathered pace.

The government’s long-term plan is to bury Britain’s nuclear waste deep underground in a geological disposal facility. The project, estimated to cost between £20bn and £53bn, would receive intermediate-level waste from nuclear facilities by 2050 and high-level waste and spent fuel from 2075.

It will echo similar projects in Sweden, France and Finland, which is nearing completion of its storage cave. A government body, Nuclear Waste Services, which is running the project, is in the process of engaging with different communities – two near Sellafield, and another near Mablethorpe on the east coast – in an attempt to win local approval for the plans.


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